CN105934603B - Leak determination on a hydraulic clutch actuator - Google Patents

Abstract

The invention relates to a clutch actuator comprising a master cylinder, a hydraulic line and a slave cylinder for actuating a clutch. The method for determining a leak at a clutch actuator comprises the steps of: determining a parameter of a clutch actuator; comparing the parameter to a predetermined threshold; determining a prompt for a leak if the parameter exceeds a threshold; and providing the prompt.

Description

Leak Determination on Hydraulic Clutch Actuators

technical field

The invention relates to a hydraulic clutch actuator. In particular, the present invention relates to determining leakage on the clutch actuator.

Background technique

The hydraulic clutch actuator includes a master cylinder and a slave cylinder, which are connected to each other via hydraulic lines. An active piston is accommodated in the active cylinder, which can be moved axially by means of an actuator. The slave piston housed in the slave cylinder reflects this movement by exchanging hydraulic fluid between the master cylinder and the slave cylinder. In this case, the driven piston is designed to actuate a clutch for transmitting torque in the drive train, in particular the drive train of a motor vehicle. In one embodiment, the clutch is closed by means of a clutch spring, and the actuation causes the clutch to disengage, so that no torque is transmitted through the clutch, while in another embodiment, the actuation causes the friction elements of the clutch to press against each other, so that the torque Can be transmitted through the clutch. In the latter mentioned case, the disengagement of the clutch is effected by means of a spring.

Of course, the hydraulic components of clutch actuators are subject to tolerances and wear. In addition, there is a temperature dependence. Therefore, in order to be able to control the opening and closing behavior of the clutch with sufficient precision by the positioning of the active piston, it is necessary to take into account disturbance factors or to calibrate the hydraulic clutch actuator from time to time.

DE 10 2012 204 929 A1 relates to a method for starting a clutch.

EP 2 516 878 A1 relates to a device and method for leak determination in an automatic electro-hydraulic clutch system. Here, leakage is determined based on hydraulic pressure in the clutch system.

Known equipment for determining leaks on clutch actuators is often expensive and may require components that are themselves subject to wear and inaccuracies. Known methods for determining leakage at hydraulic clutch actuators are generally not precise enough or cannot be performed in all driving states of motor vehicles on which clutches that can be actuated by means of the clutch actuator are used.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a method and a control device for determining leakage at a hydraulic clutch actuator. The invention achieves this object by means of a method and a clutch actuator having the features of the independent claims. The dependent claims describe preferred embodiments.

The clutch actuator includes a master cylinder, hydraulic lines and a slave cylinder for operating the clutch. A method for determining leakage on a clutch actuator includes the steps of: determining a parameter of the clutch actuator; comparing the parameter to a predetermined threshold; determining an indication of leakage if the parameter exceeds the threshold; and providing the mentioned prompt.

The invention can be used particularly advantageously on clutch actuators which are part of a powertrain, for example on a motor vehicle. By providing the indication, for example a device or program for the higher-level control of the driving strategy of the motor vehicle can be aware of this leakage. As a result, measures can be derived to keep the motor vehicle running well despite the leaks. If the clutch is, for example, part of a dual clutch on a dual clutch transmission, an attempt can be made to stop actuating the clutch as much as possible. The motor vehicle can then continue to move, preferably using the other clutch. Furthermore, a warning can be sent to the driver of the motor vehicle.

A quick and reliable determination of leakage can be achieved by a simple comparison of the parameters acquired at the clutch actuator. The matching of multiple components or parameters may be unnecessary, enabling the method to be used generically. The leak determination can be achieved quickly and the sensitivity of the leak determination can be varied by choosing the threshold accordingly.

In a first variant, the parameter refers to a shift of the clutch characteristic curve in the direction of increasing actuator travel.

The clutch characteristic curve shows how the force exerted on the clutch is related to the position of the active piston. If increased actuator travel is required to achieve a predetermined clutch force, this indicates a leak on the clutch actuator. Especially when hydraulic clutch actuators are not recalibrated, small errors can accumulate and lead to significant shifts in the clutch characteristic curve, which can be clearly and quickly demonstrated.

In order to calibrate the hydraulic clutch actuator, the bleed process can be performed in a condition-controlled or time-controlled manner. Here, the pressure in the active cylinder is brought as close to the ambient pressure as possible, and the connection to the compensation vessel at ambient pressure is opened. The compensating container contains hydraulic fluid and it enables fluid exchange between the master cylinder and the compensating container in order to establish a known initial state in the hydraulic clutch actuator after closing the connection. With the deflation process, small effects, eg, caused by leaks in the region of the driving piston and the driven piston, do not accumulate into larger effects.

In another embodiment, it is therefore proposed that the parameter includes the frequency of the gassing process. This applies in particular when the deflation process is triggered in an event-controlled manner. Existing strategies for controlling the gassing process can advantageously continue to apply. It is then possible to indirectly determine the leakage at the clutch actuator.

The parameter can also relate to the speed of movement of the clutch characteristic curve. The faster the clutch characteristic curve moves, the greater the amount of fluid that typically leaks from the closed system between the master and slave cylinders. Then, based on the speed of movement, a clear and reliable determination of indications about leakage can be achieved.

In another variant, which can be combined with the above variant, the parameter mentioned refers to the clutch force. The clutch force is the clutch operating force generated by the clutch actuator.

In one embodiment, the threshold value depends on the position of the clutch actuator. A method for controlling a clutch actuator to operate a clutch can provide a predetermined position at which a predetermined clutch force is desired. If, however, only a small clutch force is achieved at the predetermined position, an indication of the existence of a leak can be deduced.

The position of the clutch actuator can be in the region of the maximum position of the clutch actuator. Typically, the maximum position corresponds to the position of the active piston in the active piston that causes the greatest actuation of the clutch and beyond which the active piston generally cannot be driven. It is normally moved towards this position when the clutch is fully actuated. The parameters set at this location can be known for the control of the clutch actuator, and the comparison of the determined parameters with the desired parameters can be performed simply and quickly.

Furthermore, the method can comprise the steps of: actuating the clutch by means of the clutch actuator; and confirming the previously determined indication if the clutch force at any point of the actuating stroke of the clutch actuator is below a predetermined threshold value.

In other words, a test is performed in the presence of an indication of clutch leakage, which confirms the indication when the test runs positive, and otherwise negates or dismisses the indication. The actuation of the clutch can be carried out at predetermined values which are not necessary for the driving operation. In other words, the clutch is actuated in a way that is most conducive to checking for leaks.

The control device according to the invention for controlling a clutch actuator is designed to carry out the method described above, wherein the clutch actuator has a master cylinder, a hydraulic line and a slave cylinder for actuating the clutch.

Here, among other things, the control device can be designed in particular to control the actuation of the clutch as a function of a request from the driving operation. Intermediate results, parameters and expected measurements can be provided to the described method. Known control devices for clutch actuators can be extended for determining leakage at the actuator.

Description of drawings

Now, the present invention will be described in detail with reference to the accompanying drawings, wherein:

Figure 1 shows a hydrostatic clutch actuator;

FIG. 2 shows a flowchart of a method for determining leakage on the clutch actuator of FIG. 1; and

FIG. 3 shows a diagram with a clutch characteristic curve of the clutch of FIG. 1 .

Detailed ways

FIG. 1 shows a hydrostatic clutch actuator 100 . The clutch actuator 100 includes a driving side 105 and a driven side 110 . The two sides are fluidly connected to each other by means of hydraulic lines 115 .

The active side 105 includes an active cylinder 120 which is closed by means of an active piston 125 . The active piston 125 can be moved axially in the active cylinder 120 by means of the drive 130 . The drive 130 generally includes an electric motor 135, which is connected to the active piston 125 by means of a switching mechanism 140, wherein the switching mechanism 140 comprises, for example, a screw drive.

In one embodiment, a compensation container 145 is provided at the master cylinder 120, which compensation container is supplied with hydraulic fluid at ambient pressure. The connection opening 150 between the compensation container 145 and the master cylinder 120 is released by the master piston 125 when the master piston moves far enough outwards from the master cylinder 120 . Typically, the active piston 125 is moved between a zero position and a maximum position in order to operate the clutch; however, the bleed position is beyond the zero position, so that the zero position must be explicitly reached to effect the bleed process.

Preferably, a position sensor 155 is provided at the master cylinder 120 , which position sensor determines the axial position of the master piston 125 in the master cylinder 120 . A pressure sensor 160 can also be provided, which is arranged, for example, on the master cylinder 120 . The hydraulic pressure determined in this way can be used as a measure of the force exerted by the slave piston 170 on the clutch, from which the clutch force can also be determined.

The slave side 110 includes a slave cylinder 165 which is closed on one side by means of a slave piston 170 . The hydraulically connected system consisting of slave cylinder 165 , hydraulic line 115 and master cylinder 120 is filled by means of hydraulic fluid 175 . The driven piston 170 acts axially on a clutch 180 which can interrupt or communicate the flow of torque in a powertrain, especially in a motor vehicle.

In the following, without loss of generality, it is assumed that the actuation of clutch 180 is caused by moving the master piston 125 into the master cylinder 120 , whereby hydraulic fluid 175 is supplied from the master cylinder 120 via the hydraulic line 115 to the slave cylinder 165 . , and there the driven piston 170 is axially pressed against the components of the clutch 180 so that the clutch produces a torque flow. In another embodiment, the clutch 180 can also be disengaged by means of the same procedure.

The dual clutch at the dual clutch transmission can include a clutch 180, wherein the drive engine acts on two clutches 180 which drive differently sized pairs of gears, which act on a common output shaft to The drive wheels that drive the motor vehicle. In this case, usually only one of the clutches is always closed and the other is opened. The actuation of the clutch 180 and, if necessary, the switching of the engaged gear pairs can be controlled by means of the control device 185 . In particular, the control device 185 controls the drive 130 and can be connected to sensors, in particular to the position sensor 155 or the pressure sensor 160 .

There can be leaks on clutch actuator 100 that cause fluid 175 to escape from the hydraulic system, which consists of master cylinder 120 , hydraulic line 115 and slave cylinder 165 . The reason for this can be, for example, that the master piston 125 does not seal in the master cylinder 120 , or that the slave piston 170 does not seal in the slave cylinder 165 . It is also possible that leaks due to damage, damaged areas, or aging cause fluid 175 to flow outward. In order to be able to control the clutch 180 precisely, it is proposed to determine the presence of a leak by means of a method.

FIG. 2 shows a flowchart of a method 200 for determining leakage on the clutch actuator 100 of FIG. 1 . The method 200 is designed in particular to be executed on the control device 185 .

The method 200 begins in step 205 . Next, one or more of the following steps 210 to 225 can be performed sequentially or simultaneously. Here, parameters on the clutch actuator 100 are determined in each of steps 210 to 225 for later evaluation.

In step 210, a deflation frequency is determined. As described above, the bleed process involves the movement of the master piston 125 in the master cylinder 120 to the bleed position so that compensation of the fluid 175 between the master cylinder 120 and the compensation container 145 can occur. When the bleed process is triggered can be determined by the control method used to operate the clutch 180 . Preferably, the control of the bleed process is carried out based on parameters on the clutch actuator 100 , so that the bleed process is performed only when a recalibration of the clutch actuator 100 is determined based on the parameters on the clutch actuator 100 as much as possible. In step 210 of method 200, the deflation process is observed over a predetermined period of time and its frequency is determined.

The shift of the clutch characteristic curve is determined in step 215 . As mentioned above, the clutch characteristic curve describes the position of the master piston 125 in the master cylinder 120 as a function of the clutch force, which can be determined, for example, by means of the pressure sensor 160 . The characteristic curve is generally drawn two-dimensionally, wherein the increasing actuation of the active piston 125 is drawn in the horizontal direction. If the clutch characteristic curve shifts in the direction of an increase in the actuation value of the piston 125 , this can be an indication of leakage at the clutch actuator 100 .

In a variant, in step 215 the speed at which the clutch characteristic curve moves in the direction of increasing actuation travel is also measured.

In step 220, the clutch force at the maximum position of the active piston 125 is determined. The clutch force can be determined by means of the pressure sensor 160 and the maximum position of the master piston 125 is the position that requires the master piston 125 to move the furthest into the master cylinder 120 to operate the clutch 180 . This position is normally occupied in order to fully operate the clutch 180 . If the predetermined actuating force is not reached at the maximum position, this can be interpreted as an indication of a leak on the clutch actuator 100 .

In step 225 , the clutch force at any other position of the actuating stroke of the master piston 125 in the master cylinder 120 can be determined, for example, by means of the pressure sensor 160 . During actuation of the clutch 180 , the master piston 125 can move into other regions of the master cylinder 120 , wherein the actuation method of the clutch actuator 100 can expect a clutch force at a predetermined actuation position. If the clutch force is not reached, this can be evaluated as an indication of leakage.

In step 230, the results of one or more of steps 210 to 225 are compared to respective associated thresholds. If the associated threshold is exceeded, the method 200 can return to step 205 and repeat. If one or all of the recorded parameters do not reach their associated thresholds, then it is determined that there is an indication of a leak.

This indication can optionally be checked again by actuating clutch 180 in step 235 . It is necessary for this to apply for permission from a higher-level program in order to actuate clutch 180 . The superordinate program can be designed in particular for controlling the driving strategy, for example for selecting an engaged gear in the drive train of the motor vehicle in which the clutch 180 is arranged. If permission is given, the actuation of clutch 180 can preferably go from a completely unactuated position into a maximum position.

At one or more positions during maneuvering, the clutch force is determined, for example, by means of a pressure sensor 160 . It can then be determined in a subsequent step 240 whether the clutch force in the one or more positions exceeds a predetermined value. In a further embodiment, a minimum value is specified, which should not fall below any position of the active piston 125 . If sufficient clutch force is always provided, method 200 can return to step 205 and repeat. Otherwise, a report is provided in step 245 that there is an indication of a leak on the clutch actuator 100 .

The confirmation of the decision of step 230 in steps 235 and 240 can also be skipped, so that a report is provided in step 245 directly after step 230 . After step 245, the method 200 can return to step 205 and proceed again.

FIG. 3 shows a diagram 300 with an exemplary clutch characteristic curve 305 . The position 310 of the clutch actuator 100 or of the master cylinder 125 is plotted in the horizontal direction, and the clutch force 315 is plotted in the vertical direction. Maximum clutch force is typically achieved at the maximum position 315 of the active piston 125 .

List of reference signs

100 clutch actuator

105 Active side

110 Driven side

115 Hydraulic lines

120 Active Cylinder

125 Active Piston

130 drives

135 Electric motors

140 Conversion mechanism

145 Compensation container

150 Connection openings

155 Position Sensor

160 pressure sensor

165 Slave Cylinder

170 driven piston

175 Hydraulic fluid

180 clutch

185 Controls

200 methods

205 start

210 Determine the deflation frequency

215 Determine the shift of the clutch characteristic curve

220 Determine the clutch force at the maximum position

225 Determine clutch force

230 Leak speculation?

235 Operating the clutch

240 enough clutch force?

245 Provide reports

300 charts

305 clutch characteristic curve

310 Locations

315 clutch force

320 maximum position

Claims (6)

1. A method (200) for determining a leak on a hydraulic clutch actuator (100), wherein the clutch actuator (100) comprises a master cylinder (120), a hydraulic line and a slave cylinder (165) for operating a clutch (180), and the method (200) comprises the steps of:

-determining (210) parameters of the clutch actuator (100), the parameters comprising at least one of: a speed of movement of the clutch characteristic (305) when the clutch characteristic (305) moves in a direction of increasing actuator travel;

-comparing (230) the parameter with a predetermined threshold;

-determining (230) a prompt for a leak if the parameter exceeds the threshold; and

-providing (245) the prompt.

2. The method (200) of claim 1, wherein the parameter further comprises a clutch force (315).

3. The method (200) of claim 2, wherein the threshold value is dependent on a position (310) of the clutch actuator (100).

4. The method (200) of claim 3, wherein the position (310) of the clutch actuator (100) is within a range of a maximum position of the clutch actuator.

5. The method (200) according to any one of the preceding claims, further comprising the step of:

-manipulating (235) the clutch by means of the clutch actuator (100); and

-confirming (240) the prompt if a clutch force (315) at any position of a manipulation stroke of the clutch actuator (100) is below a predetermined threshold.

6. A control device (185) for controlling a clutch actuator (100), the clutch actuator (100) having a master cylinder (120), a hydraulic line (115) and a slave cylinder (165) for actuating a clutch (180), wherein the control device (185) is designed for carrying out the method (200) according to one of the preceding claims.

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